Abstract. We present here a dynamical method for modelling temporal and geographical
variations in ammonia emissions in regional-scale chemistry transport models
(CTMs) and chemistry climate models (CCMs). The method is based on the
meteorology in the models and gridded inventories. We use the dynamical
method to investigate the spatiotemporal variability of ammonia emissions
across part of Europe and study how these emissions are related to
geographical and year-to-year variations in atmospheric temperature alone.
For simplicity we focus on the emission from a storage facility related to a
standard Danish pig stable with 1000 animals and display how emissions from
this source would vary geographically throughout central and northern Europe
and from year to year. In view of future climate changes, we also evaluate the
potential future changes in emission by including temperature projections
from an ensemble of climate models. The results point towards four overall
issues. (1) Emissions can easily vary by 20% for different geographical
locations within a country due to overall variations in climate. The largest
uncertainties are seen for large countries such as the UK, Germany and
France. (2) Annual variations in overall climate can at specific locations
cause uncertainties in the range of 20%. (3) Climate change may increase
emissions by 0–40% in central to northern Europe. (4) Gradients in
existing emission inventories that are seen between neighbour countries
(e.g. between the UK and France) can be reduced by using a dynamical
methodology for calculating emissions. Acting together these four factors can
cause substantial uncertainties in emission. Emissions are generally
considered among the largest uncertainties in the model calculations made
with CTM and CCM models. Efforts to reduce uncertainties are therefore highly
relevant. It is therefore recommended that both CCMs and CTMs implement a
dynamical methodology for simulating ammonia emissions in a similar way as
for biogenic volatile organic compound (BVOCs) – a method that has been used
for more than a decade in CTMs. Finally, the climate penalty on ammonia
emissions should be taken into account at the policy level such as the NEC
and IPPC directives.